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UCSS is rare and often associated with LSVC. There are 62.9% (100/159)
patients with LSVC in our series. The hemodynamic changes of UCSS depend
on: (1) the presence of LSVC; (2) whether the CS opening is expanded,
constricted or occluded; (3) whether there is a communication between
the CS and the LA; (4) whether there are associated malformations such
as the blood flow obstruction in the left or right atrioventricular
system[3]. In our series, only 18 cases were sole UCSS, the
remaining 141 cases were associated with other intracardiac
malformations, the most common ones were associated ECD (40.9%,
65/159). Most clinical manifestations of UCSS should be analyzed
comprehensively in combination with other associated cardiac
malformations.